It is known that, in order to cause a wireless base station not supporting the adaptive array to support the adaptive array, a replacement of the baseband unit is required. FIG. 3 shows a structure of a conventional wireless base station that does not support the adaptive array. FIG. 4 shows a structure of a conventional wireless base station that supports the adaptive array.
As shown in FIG. 3, a baseband unit 300, which performs an omnidirectional communication, includes a MAC processing unit 301, a signal modulation unit 302, an inverse FFT (Fast Fourier Transfer) unit 303, a CP (Cyclic Prefix) attaching unit 304, a signal demodulation unit 305, a FFT (Fast Fourier Transfer) unit 306, and a CP removing unit 307. The signal modulation unit 302, inverse FFT unit 303, and CP attaching unit 304 are functional units that function only when a signal is transmitted, and the signal demodulation unit 305, FFT unit 306, and CP removing unit 307 are functional units that function only when a signal is received. When the wireless base station shown in FIG. 3 is caused to support the adaptive array, it is necessary to replace the baseband unit 300.
FIG. 4 is a functional structure diagram of the wireless base station in which the baseband unit 300 has been replaced with the baseband unit 400, includes as many radio units as the number of antennas, and supports the adaptive array. The baseband unit 400 includes a MAC processing unit 401, a signal modulation unit 402, inverse FFT units 404 and 406, CP attaching units 405 and 407, a signal demodulation unit 412, FFT units 414 and 416, and CP removing units 415 and 417.
As understood by comparing FIG. 3 with FIG. 4, in order to support the adaptive array, as many inverse FFT units, CP attaching units, FFT units, and CP removing units as the number of antennas are required.
Patent Literature 1 discloses a wireless base station that can switch between the adaptive array and the omnidirectional communication.